White LED, and backlight and liquid crystal display device using the same

1. A white LED, comprising:

a light emitting element with a light emission peak wavelength in a range of 380 to 420 nm; and

a phosphor layer containing three or more types of phosphors including at least a blue phosphor, a green phosphor, and a red phosphor,

wherein the phosphor layer has a first phosphor layer containing a mixture of the green phosphor and the red phosphor, and a second phosphor layer containing the blue phosphor and disposed on an opposite side of a side of the light emitting element of the first phosphor layer;

wherein a content of the blue phosphor in an entire phosphor contained in the first phosphor layer is 5 mass % or less, or the blue phosphor is not contained in the first phosphor layer,

wherein a content of phosphor other than the blue phosphor in an entire phosphor contained in the second phosphor layer is 5 mass % or less, or no phosphor other than the blue phosphor is contained in the second phosphor layer,

wherein a ratio of a content of the green phosphor to a content of the red phosphor in the first phosphor layer is in a range of 0.05 to 0.4, and

wherein a ratio of a thickness of the second phosphor layer to a thickness of the first phosphor layer is in a range of 1 to 3.

2. The white LED as set forth in claim 1 ,

wherein the first phosphor layer does not contain the blue phosphor, and the second phosphor layer does not contain the green phosphor or the red phosphor.

3. The white LED as set forth in claim 1 ,

wherein the blue phosphor comprises at least one selected from an europium-activated halophosphate phosphor with a composition represented by a general formula (1):

(Sr 1-x-y-z Ba x Ca y Eu z ) 10 (PO 4 ) 6 .X 2   (1)

where, X is at least one element selected from F, Cl and Br, x is a value satisfying 0≦x<0.2, y is a value satisfying 0≦y<0.1, and z is a value satisfying 0.005<z<0.1, and

an europium-activated aluminate phosphor with a composition represented by a general formula (2):

(Ba 1-x-y-z Sr x Ca y Eu z )MgAl 10 O 17   (2)

where, x is a value satisfying 0≦x<0.5, y is a value satisfying 0≦y<0.1, and z is a value satisfying 0.15<z<0.4,

wherein the green phosphor comprises an europium/manganese-activated aluminate phosphor with a composition represented by a general formula (3):

(Ba 1-x-y-z Sr x Ca y Eu z )(Mg 1-u Mn u )Al 10 O 17   (3)

where, x is a value satisfying 0≦x<0.5, y is a value satisfying 0≦y<0.1, z is a value satisfying 0.15<z<0.4, and u is a value satisfying 0.25<u<0.6, and

wherein the red phosphor comprises an europium-activated lanthanum oxysulfide phosphor with a composition represented by a general formula (4):

(La 1-x-y Eu x M y ) 2 O 2 S  (4)

where, M is at least one element selected from Sb, Sm, Ga and Sn, x is a value satisfying 0.08<x<0.17, and y is a value satisfying 0≦y<0.003.

4. The white LED as set forth in claim 1 ,

wherein the light emission peak wavelength of the light emitting element is in a range of 390 to 410 nm.

5. A backlight, comprising:

a plurality of the white LEDs as set forth in claim 1 ; and

a substrate to which the plurality of white LEDs are mounted.

6. A liquid crystal display device, comprising:

a backlight comprising a plurality of the white LEDs as set forth in claim 1 , and a substrate to which the white LEDs are mounted; and

a liquid crystal panel disposed in a light emitting surface side of the backlight.

7. The white LED as set forth in claim 1 ,

wherein the first phosphor layer comprises a first transparent resin layer and the phosphor dispersed in the first transparent resin layer, and a content of the phosphor contained in the first phosphor layer is in a range of 30 to 80 mass %, and

wherein the second phosphor layer comprises a second transparent resin layer and the phosphor dispersed in the second transparent resin layer, and a content of the phosphor contained in the second phosphor layer is in a range of 30 to 80 mass %.

8. The white LED as set forth in claim 7 , further comprising:

a third transparent resin layer not containing a phosphor and sealing the light emitting element,

wherein the first transparent resin layer of the first phosphor layer is formed on an outer surface of the third transparent resin layer, and the second transparent resin layer of the second phosphor layer is formed on an outer surface of the first transparent resin layer.

9. The white LED as set forth in claim 1 ,

wherein a thickness of the first phosphor layer is in a range of 1000 to 3000 μm, and

wherein a thickness of the second phosphor layer is in a range of 1000 to 9000 μm.